#include <stdio.h>
#define  M 5
#define  N 100
int main()
{
    //注释xxxxxxxxx
    for(int i = 0; i < M; i++)
    {
        printf("hello world!\n");
    }

#ifdef N
    printf("N = %d\n", N);
#else
    printf("No N");
#endif
    return 0;
}


